JPS62123788A - Variable wavelength type laser oscillator - Google Patents

Abstract

PURPOSE:To eliminate an injection laser oscillator and an optical system by a method wherein a wavelength selecting element is provided outside the concave mirror of an unstable resonator and a laser beam with a required wavelength is selectively reflected by the wavelength selecting element and injected into the unstable resonator. CONSTITUTION:When a laser medium 11 starts oscillation, a natural emitted light with a low output intensity and a wide wavelength range is introduced to a prism 6, which is a wavelength selecting element, through the light transmitting part 13b of a concave mirror 13. Only the wavelength component of the natural emitted light which enters vertically to a reflective surface 6a returns into an unstable resonator through the light transmitting part 13b of the concave mirror 13 along the same light path as the incident path and an initial laser oscillation is created between a convex mirror 12 and the prism 6. The light emitted by this oscillation is a single wavelength laser beam and is resonated and amplified between the convex mirror 12 and the concave mirror 13 without changing its spectral properties and outputted from the non-coated part 12b of the convex mirror 12 as a laser beam of high output.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an improvement in a wavelength tunable laser oscillation device capable of selectively oscillating and outputting laser beams having different wavelengths.

[Technical background of the invention]

Conventionally, one using an injection locking method is known as one of this type of devices. Figure 3 (a
> shows the configuration of a laser oscillation device to which this injection locking method is applied, and this device has high reflection coatings 2a and 3a applied to opposite ends of a laser medium 1 having broadband oscillation characteristics, respectively. A convex mirror 2 and a concave mirror 3 are arranged to form an unstable resonator, and a low-output injection laser oscillator 4 is provided, and the laser beam output from the laser oscillator 4 is transmitted through an optical system 5. The injection is carried out into the unstable resonator through the transparent part 3b provided on the optical axis of the concave mirror 2, thereby locking the oscillation wavelength of the unstable resonator to the wavelength of the injection laser beam. The oscillation laser beam having the same wavelength is transmitted from the non-reflection coating portion 2b of the convex mirror 2 at high output. Incidentally, FIG. 3(b) shows a beam pattern of the oscillation output laser light. Such a device is very useful because it can selectively emit only a desired wavelength of laser light from the laser medium 1 with energy dispersed over a wide band at a high output.

C. Problems of Background Art] However, in such a conventional wavelength tunable laser oscillator, an injection laser oscillator 4 must be provided to cause injection locking, and the injection laser beam may become unstable. Since the optical system 5 is required to be introduced into the resonator, the structure is complicated and large, which has the drawback of making the device extremely expensive.

[Purpose of the invention]

The present invention eliminates the need for large-scale components such as an injection laser oscillator and optical system, and thereby enables a wavelength tunable laser oscillation that is simple, compact, and inexpensive to obtain high-output narrowband laser light. The purpose is to provide equipment.

[Summary of the invention]

In order to achieve the above object, the present invention disposes a wavelength selection element outside the concave mirror of the unstable resonator, and uses this wavelength selection element to move the unstable resonator from the optical axis of the concave mirror. Of the laser light emitted through the optical part, laser light of a desired wavelength is selectively reflected and injected into the unstable resonator through the transparent part of the concave mirror. This is designed to cause locking of a desired wavelength.

[Embodiments of the invention]

FIG. 1(a) shows the configuration of a wavelength tunable laser oscillation device according to an embodiment of the present invention, and numeral 11 indicates a laser medium having broadband oscillation characteristics. A convex mirror 12 and a concave mirror 13, which constitute an unstable resonator, are disposed at both ends of the laser medium 11, respectively. These convex mirror 12 and concave mirror 13 each have a high reflection coating applied to their mutually opposing laser reflecting surfaces.

Further, an anti-reflection coating 12b is applied to the outer peripheral portion of the laser reflecting surface of the convex surface [12], and the oscillated laser beam is output from this portion. Further, a light transmitting portion 13b having a predetermined diameter is provided at the optical axis portion of the concave mirror 13.
Laser injection is performed from b.

Now, on the optical axis outside the concave mirror 13, a prism 6 as a wavelength selection element is arranged. The prism 6 includes a wavelength selection surface 6b and a reflection surface that reflects the laser beam incident through the wavelength selection surface 6b, and this reflection surface is coated with a high reflection coating 6a. still,
This reflective surface is formed into a concave surface, and its curvature is set by the curvature of the reflective surface of the convex mirror 12 and the optical path length from this reflective surface to the wavelength selection surface 6b of the prism 6. Further, the prism 6 is supported so as to be swingable in the direction of the arrow by an angle adjustment mechanism (not shown), and this swinging allows the reflection angle of the laser beam to be varied.

With such a configuration, when the laser medium 11 starts oscillating, spontaneously emitted light with low output and a wide wavelength range is transmitted to the concave mirror 13.
The light is guided to the prism 6 through the transparent portion 13k). Then, as shown in FIG. 2, for example, the spontaneously emitted light 7 with a wide wavelength width is refracted by the wavelength selection surface 6b of the prism 6 with a different refractive index for each wavelength, and then enters the prism 6, and then is reflected by the reflection surface 6a. It is reflected and returns to the concave mirror 13. At this time, among the spontaneously emitted light of each wavelength, only the spontaneously emitted light 7a of the wavelength component that is perpendicularly incident on the reflective surface 6a passes through the same path as the incident path from the transparent part 13a of the concave mirror 13 into the unstable resonator. Then, initial laser oscillation with a selected wavelength occurs due to resonance between the convex mirror 12 and the reflective surface 6a of the prism 6. As a result, the unstable resonator is
This is equivalent to injecting a single wavelength laser beam from an external injection laser oscillator, and this causes the prism 6 to
The oscillation wavelength is locked to the laser beam incident from the laser beam, and only the laser beam of this wavelength is resonantly amplified between the convex mirror 12 and the concave mirror 13 without changing its spectral properties, and is emitted from the convex mirror 12 as a high-power laser beam. It is output from the non-coating section 12b. FIG. 1(b) shows the beam pattern of the output laser light. By the way,
The output energy of the above laser beam is, for example, an XeF (C-+A) laser that can obtain a laser beam of 50 mJ at 460 to soon m (wavelength width 40 nm) when oscillated in a wide band without setting equivalent restrictions. When used as a medium, a narrow band laser beam with a wavelength width of 0.5 nllll and an output energy of 50 to 60 mJ can be obtained.

In this way, in this embodiment, by combining the unstable resonator and the prism 6 as a wavelength selection element, a high-output laser beam with a desired wavelength can be generated, just like when using an injection laser oscillator. can be generated, and can be realized with an extremely simple configuration without using an injection laser oscillator or an injection optical system as in the past, and as a result, a small and inexpensive device can be provided. I can do it.

Furthermore, in this embodiment, the prism 6 is supported by an angle adjustment mechanism so that the reflection angle can be variably set.
Laser light of a desired wavelength can be easily obtained by simply adjusting the reflection angle of the prism appropriately using this angle adjustment mechanism.

Note that the present invention is not limited to the above embodiments. For example, instead of a prism, a grating may be used as the wavelength selection element. In addition, various modifications may be made to the configuration of the unstable resonator, the type of laser medium having broadband oscillation characteristics, the configuration of the wavelength selection element, etc. without departing from the gist of the present invention.

〔Effect of the invention〕

As described in detail above, according to the present invention, a wavelength selection element is disposed outside the concave mirror of the unstable resonator, and the wavelength selection element allows the unstable resonator to be connected to the transparent mirror provided on the optical axis of the concave mirror. Of the laser light emitted through the optical part, laser light of a desired wavelength is selectively reflected and injected into the unstable resonator through the transparent part of the concave mirror. By causing locking of the desired wavelength, large-scale components such as an injection laser oscillator and an optical system can be eliminated. It is possible to provide a wavelength tunable laser oscillation device that can obtain a single laser beam over a wide range of wavelengths.

[Brief explanation of drawings]

FIGS. 1(a), (b), and 2 are for explaining a wavelength tunable laser oscillation device according to an embodiment of the present invention, and FIG. 1(a) is a diagram showing the configuration of the device. , Figure 1 (
b) is a diagram showing the beam pattern of the output laser beam, FIG. 2 is an enlarged diagram for explaining the operation of the prism, and FIG.
) and (b) are for explaining a conventional wavelength tunable laser oscillation device, (a> is a diagram showing the configuration of the device, and (b) is a diagram showing the configuration of the device.
) is a diagram showing a beam pattern of output laser light. 11... Laser medium having broadband oscillation characteristics, 12...
...Convex mirror, 12a...High reflection coating part, 12
b... Anti-reflection coating part, 13... Concave mirror, 1
3a... High reflection coating part, 13b... Transparent part, 6... Prism, 6a... Reflective surface, 6b... Wavelength selection surface, 7... Laser light. Applicant's agent Patent attorney Takehiko Suzue (a) (b) Figure 1 Figure 2 Figure 3

Claims (2)

[Claims] (1) A laser medium that oscillates a broadband laser beam, a convex mirror having a laser output section disposed on one end of the laser medium, and a convex mirror having a light-transmitting section on the optical axis and disposed on the other end of the laser medium. A concave mirror arranged to form an unstable resonator together with the convex mirror and a laser beam of a desired wavelength guided from the light-transmitting part of the concave mirror arranged outside the concave mirror are selected, and a laser beam of a desired wavelength is selected from the light-transmitting part. What is claimed is: 1. A wavelength tunable laser oscillation device comprising: a wavelength selection element for injecting into an unstable resonator through a wavelength selection element. (2) The wavelength-tunable type according to claim (1), wherein the wavelength selection element is composed of a prism having a reflective surface for the selective laser beam, and the reflection angle by the reflective surface is variable. Laser oscillation device.